He said his university, which produces about half of all Danish engineering research, had made a conscious effort to increase its international links. "We have also been very selective about who we collaborate with. It is like tennis: you get better only if you play with someone who is as good as or slightly better than you."

However, he voiced concern that Denmark's output of papers was less than half that of Singapore. "If we could combine the quality with greater volume, that would really be a big contribution to Denmark," he added.

A spokeswoman for the Swiss Academy of Engineering Sciences put Switzerland's high ranking down to its "first-rate" education system in maths and engineering, as well as its culture of "valuing and rewarding" engineering achievement.

Sue Ion, a Fellow of the Royal Academy of Engineering, said citations were not the best way to judge the quality of engineering research. "There is a reluctance (among engineers) to spend time writing papers rather than coming up with solutions and fixing things," she said.

Barry Clarke, president of the Engineering Professors' Council, said figures for civil engineering showed that the UK had outperformed most countries with a similar research profile over the past decade, obtaining the highest proportion of citations in the best journals.